ASME Section VIII Div.1 formed head straight flange (skirt) design for external loads

[pat7987]

Hello,

Shall thickness calculation for external pressure and longitudinal /circumferential stresses due to wind, seismic/weight loads for straight flange of heads (head skirt) shall be produced separately, if design program is not explicitly reporting the same?

Some other threads: https://www.eng-tips.com/threads/head-straight-flange-thickness.219411/ AND https://www.eng-tips.com/threads/why-does-compress-increase-my-shell-thickness.194228/

 

[r6155]

ASME VIII-1 is very clear, didn't you read it?.

 

[Trestala]

if design program is not including the same? Is it mandatory to perform these calculations for vessel under vacuum design with wind and seismic loads applicable?

Commercial softwares such as Compress and PVElite already does this for the straight flange of heads.

 

[jt1234]

pat7987, I probably knows what you are confused. So making it simple for you: head skirt or straight flange is part of the shell. It will be treated as shell to resist all kinds of loading including external pressure, wind / seismic, you name it. Commercial softwares have taken care of this.
However, commercial softwares, Compress and PV Elite included, are lack of the accuracy to calculate stress at the skirt to head junction when support skirt is attaching to spherical head, which normally has half of the shell thickness.

 

[KevinNZ]

A bit OT, but I have seen vessel designers get caught out with commercial software because the skirt design does not include the loads from external piping attached to the vessel. e.g EQ calculation only uses the weight of the vessel and does no add the EQ loads from attached piping.

We head this off by providing the vessel designer the skirt loads from the pipe stress model, which includes the vessel and an anchor at the skirt.